A medical suture needle (hereinafter referred to as a suture needle) has a sharp tip at its leading end portion. There are a needle having plural cutting edges arranged from this sharp tip, and a needle having a cross-section formed into generally a circle from the sharp tip without having a cutting edge. Various standards are set for a shape or thickness I and various types of suture needles are provided for every standard. A doctor appropriately selects one of these suture needles according to the various conditions such as a living tissue or a region that should be sutured.
A needle having cutting edges is formed to have a cutting portion formed at its leading end portion, a body portion formed continuous with the cutting portion, and a proximal end part that is formed continuous with the body portion and is provided with a hole for connecting a suture thread. The body portion is a portion that should be gripped by a needle holder during an operation, and the cross-section thereof is formed into a polygon including a triangle. The proximal end part includes the one having a cross-section that is formed into an ellipse corresponding to the shape of the hole for connecting the suture thread, and the one having the cross-section formed into a circle.
The suture needle in which the cross-section of the body portion has a polygonal shape including a triangular shape as described above is generally formed by press-molding the body portion. The suture needle in which the cross-section of the cutting portion is polygonal including a triangle shape is formed as described below. Specifically, the portion corresponding to the cutting portion is roughly formed by a press working, and then, the respective surfaces are ground to form cutting edges at the intersection part of the respective surfaces. Alternatively, plural surfaces are formed by grinding without performing a rough forming through the press working, and cutting edges are formed at the intersection part of the respective surfaces.
A representative example of the suture needle described above will be described with reference to FIGS. 6 and 7. A suture needle 50 illustrated in FIG. 6 is a so-called R needle. It is made as a curved needle (see FIG. 1) that is curved with a curvature set beforehand. A sharp tip 51 is formed at its leading end, and three cutting edges 52 are formed from the sharp tip 51. The respective cutting edges 52 are formed by the intersection of two grinded surfaces 53. The portion including the sharp tip 51 and the cutting edges 52 is formed into a cutting portion 55, and the portion continuous with the cutting portion 55 is formed as a body portion 56 having a triangular cross-section. A proximal end part 57 that couples a suture thread is formed continuous with the body portion. In the suture needle 50, the sharp tip 51 is formed so as to agree with the center of the thickness.
In the suture needle 50 described above, all of three surfaces of the cutting portion 55 are the grinded surfaces 53. However, there has been known a suture needle in which two surfaces are defined as pressed surfaces formed by a press-molding, and one surface is formed as a grinded surface, wherein a cutting edge is formed at the intersection of the pressed surface and the grinded surface. When one surface is formed as the grinded surface as described above, the surface is heavily ground after the press to sharpen the cutting edge, in order to afford sharpness.
A suture needle illustrated in FIG. 7 is a so-called P needle. Like the R needle, a sharp tip 51 is formed at the leading end, wherein three cutting edges 52 are formed from the sharp tip 51, and the respective cutting edges 52 are formed by the intersection of two grinded surfaces 53. The portion including the sharp tip 51 and the cutting edge 52 is formed as a cutting portion 55, and the portion continuous with the cutting portion 55 is formed as a body portion 56 having an elliptic cross-section formed by a press-forming. A proximal end part 57 that couples a suture thread is also formed continuous with the body portion 56. In the suture needle SO, the sharp tip 51 is formed so as to agree with the center of the thickness.
The invention described in Patent Document 1 relates to a suture needle that passes through a calcified living tissue or bone for use. This suture needle has plural flat surfaces for forming one or more cutting edges at the cut part. The cutting edge is converged toward the sharp tip, and two or more another crossing flat surfaces for forming additional cutting edges are formed at the sharp tip. This suture needle can relatively easily pass through a hard living tissue.
On the other hand, there has been proposed, as a material of the suture needle, the one in which an austenitic stainless steel is subject to a cold wiredrawing process with a predetermined reduction of area, whereby a work hardening is generated to enhance hardness, and an austenitic structure is elongated in a fiber to enhance bending strength. When the suture needle is produced with the use of this material, a generation of rust can be prevented during a distribution, thus advantageous.
[Patent Document 1]
Japanese Patent Application Publication No. 3-70493